60 Second STEM: Conductivity Tester
Updated: Feb 10, 2020
1. Tear and fold aluminum foil into two thin strips.
2. Test the LED to find which orientation it lights up in and then flatten it so that the legs stick out to either side of the bulb.
3. Tape the positive leg to the positive side. Note: this should be the long side.
4. Wrap one of the foil strips about a quarter of the way down the popsicle stick such that foil wraps around the stick but leaves a long leg hanging.
5. Tape the negative side of the battery to the foil wrapping making sure that the battery is in contact with the foil.
6. Wrap the remaining foil strip around the other LED leg so that there is good contact between the LED leg and the foil.
7. Test your circuit by touching the foil strips to one another--it should light up! If it does not, check to make sure that you have the LED facing the correct direction and that there is good contact between the foil and leg/battery.
8. To test the object, place them so that they bridge the two leg of the foil. If an object is conductive, the LED will light up.
Make it an experiment:
Either make a prediction prior to testing or try changing something about the object you are testing to make it conductive. For example, if you test water it will not be very conductive (the light should be very dull if it lights up at all) but you might be able to add something to it to make the light brighter such as salt, sugar or lemonade mix. Try adding different amounts of whatever you choose to test to see if it changes the brightness of the light.
With this investigation, we are exploring conductivity. Conductivity is the property of materials to be able to allow electricity to pass through them. A conductive material conducts electricity like a conductor lets people travel on a train.
In this investigation, we are using an open circuit to test conductivity. A circuit is basically a circle around which electricity travels. All circuits have a power source-- a battery in our case-- a load--the LED-- and a conductive material. A closed circuit is one that electricity can travel all the way around where as an open circuit has a hole. We built an open circuit and tried to close it with different objects but only a conductive object can close the circuit.
Click here to watch Hannah from Shoestring Science explain and complete this investigation